Comparing Your Water Treatment Options: Part 1

Choosing the best way to treat your backcountry water can be tough. From pump filters to UV light, the market is full of options, and navigating today’s advanced technologies can be intimidating. But each treatment method has its pros and cons depending on the type of water you expect to encounter. In this two-part series, we’re helping you understand how each method works and what it’s designed to do—so you can make the decision that’s right for you and the water you might find.

First, it’s important to know the difference between a microfilter and a purifier. Microfilters are typically designed to remove protozoan parasites (like cryptosporidium and giardia), as well as bacteria. Microfilters are generally considered sufficient for backcountry travelers in U.S. and Canadian wildernesses. A purifier, by definition, removes the threat of bacteria, protozoa andviruses. International travelers and those stocking emergency kits should seek out a purifier, as the risk of viral infection is greater in areas where human waste can contaminate water sources.

How Devices Remove Threats: What’s Happening Inside?

Ceramic Element

Next, you can think of the treatment devices in this article as two parts: the filter element inside that cleans the water; and the part of the device that controls how the water is forced through that filter element (the device’s “form factor”).

The technologies that make up the filter element are called filter media and vary from device to device. Some are more reliable than others in certain conditions. Here’s a look at the most common types of filter media and how they clean your water:

Hollow fiber technology: Think of a bundle of tiny straws, each full of microscopic pores. Their walls allow water to flow through, but block the harmful pathogens and dirt. Because the fibers physically remove the contaminants, hollow fiber technology is very reliable for treating many real-world water conditions. Hollow fibers offer very high flow rates, but some can be damaged by drops or freezing temps.

Ceramic: Typically a cylinder with a maze of microscopic holes that also physically block the contaminants. Ceramic cartridges don’t offer as much surface area, resulting in a slower flow rate. But even heavy clogging can be quickly reversed with a little scrubbing.

Activated Carbon: A block or granulated core. Carbon works by adsorption, attracting contaminants to its surface where they get stuck. Carbon is great for removing secondary contaminates like tastes and odors. But it can lose effectiveness when flow rates or contamination levels are high. Therefore, MSR does not rely on it for removing the immediate threats.

Silica Depth: An old term for a ceramic filter.

Other Adsorptive Media: If a device doesn’t use one of the above, it likely uses some technology that relies on adsorption. Like carbon, adsportive media are good for reducing tastes and odors from clear water. But they are not reliable for most backcountry water. If water contains particles like sediment, these filters can become overwhelmed quickly, allowing threats through. More, they don’t indicate when they’re “full,” so you never know whether your filter is still doing its job.

Comparing Your Treatment Device Options

Now that you know how the water is cleaned, let’s look at your options for moving it through the filter—these are the forms you’ll see on the shelf.

Pump Microfilters/Purifiers

The pump is one of the most common and highly trusted forms. A hand pump forces water through the filter element. The element is oftentimes ceramic, hollow fiber, glass fibers, or cellulose. Some also have a layer of carbon to remove tastes and odors.

Their durability, reliability and ease of use have made them the mainstay of backcountry travelers for decades. They often remove sediment as well as the pathogens, making them ideal for situations when you’re not sure what kind of water—clear, turbid, silty—you’ll find.

Most pumps have flow rates around 1 liter per minute. The majority are compact and about 16 oz. or less. A great one will feature a cartridge that can treat over 1,000 liters. Each MSR pump can be cleaned in the field and those with hollow fiber cartridges offer an in-field integrity test.

The downside to pumps? You must remain by the water source and do the pumping yourself. Traditionally, they’re best suited for solo travelers and pairs.

Gravity Filters

Photo by Scott Rinckenberger

Gravity filters are fast, easy and practically do all the work for you. They’re so effortless that many people are instant converts. Their filter mechanism is similar to a pump, but here, gravity forces the water through. You do have to find a tree branch or other way to elevate the dirty reservoir so that gravity can pull the water down. Reliable filters often use hollow fiber or glass fiber, but other media exist.

Like pumps, gravity filters are great for wilderness travelers. They’re ideal for groups and basecamps because they often hold up to several liters. Most are pretty fast, but their real advantage lies in filtering your water all while you set up camp or prep meals.

Gravity filters roll up compact and often weigh less than a pump. In general, their cartridges don’t last quite as long, but using the clearest water possible helps increase their longevity. Most can be cleaned to maintain high flow rates. Those that use hollow fiber can be damaged by freezing or drops, so it’s good to look for one that offers an in-field integrity test, like the MSR AutoFlow microfilter.

Bottle / Squeeze / Drink-Thru Filters

The main advantage of this class of small, personal filters is low cost and complexity—the drinking bottle, collection bag, or straw, and its filter element are contained in one unit. These devices are meant for fast and light performance and/or ultimate convenience. They offer limited capacity and flow rates, so they’re best suited for individuals on day activities, like hiking, running or mountain biking, or as back-up filters.

Many of the options available use adsorptive media (carbon, coconut shell carbon, etc.), so they are not a reliable way to remove the harmful microorganisms; though some do use hollow or glass fiber.

The squeeze and drink-thru filters can be ultralight. The bottles are about a half pound or less. Although the convenience factor is very high, these devices can sometimes sacrifice practical functionality:

Water collection can be awkward, such as lying in the dirt to reach the water source.

You may have to carry around the dirty collection bag.

You may not be able to fill up other containers with the water you treat.

They generally don’t offer integrity tests.

Often they’re single-person devices, so everyone in the group must carry their own.

So how do you choose the best option for you?

Do your homework. First, understand which technology the device uses to clean your water. Because some do not reliably remove pathogens, it’s important to evaluate the technology if you’re headed into the backcountry or anywhere microorganisms are a concern. Then, it’s really just up to you to decide which form factor best suits your needs, preferences and types of adventures.

6 thoughts on “Comparing Your Water Treatment Options: Part 1”

Hands down the gravity system is the easiest and laziest to use. Try it one time and you will be converted. The price is steep, but once you see how easy it is use, you’ll understand that the extra $60-80 investment was totally worth the money!

Besides, who wants to hand pump water (or squeeze) out of stream just to get 32 ounces fluid in a Nalgene bottle after they hiked 8-12 miles with a 50+lbs pack? Not me! In the same time span it takes to use a pump for 32 oz of water, my platypus gravity system has filtered 4 Liters of water leaving me to setup my tent and build a camp fire. Oh yeah the filter is good for like 1,000 or so Liters and Gravity system folds up nicely and weights less than 1.5 lbs when empty.

On a thru hike I carry a filter and 0.5 ounce bottle of bleach (enough for 2 gallons a day for 2 weeks). Hey, if bleach is good enough for city treatment, and US States recommendation for treating well water, as well as the FDA, then it’s good ‘nuf for me.

Make sure your bleach is at the proper potency threshold. Use test strip (dirt cheap) before your trip, or just make a gallon with the dry calcium hypochlorite. Oh yeah, 2 drops per quart/liter make bleach about the cheapest thing to use (1 gallon of bleach @ $1.50 will purify 3,800 gallons of water). Put drops in water. Wait 1/2 hour. Enjoy (no, it doesn’t smell like bleach… if it does, then you have used way too much).

I use the in-line filter type, when the water is cloudy. With in-line, there’s no pumping, no waiting, just fill the water bladder, and sip like using a straw.

You might want to read this article if you are using bleach anywhere cryptosporidium is a possibility (see link below). The summary quote “C. parvum oocysts are resistant to chlorine, which is normally used in water treatment” and by resistant they say “did not reduce the infectivity after a 33-min exposure”. In short, still a good idea to use a filtering mechanism that will remove the oocysts. http://aem.asm.org/content/68/5/2576.full